JP2003094745A - Inkjet recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a good recorder image by a method wherein sudden variation of a paper gap at the time when a rear edge of a paper passes through a conveyance roller is prevented at printing on the rear edge of the paper, thereby preventing the discontinuity of the image. SOLUTION: A member for restricting a height of a face of a paper at an upstream side of a recording head is provided such that the restriction can be released. The restricting member is of a pinch roller or a paper pressing member. A sensor capable of detecting the rear edge of the paper is provided. After the rear edge of the paper is detected, the restriction of the paper at the upstream side of the head is gradually released, and thereby the deformation of the paper is gradually accepted. At last, the rear edge of the paper is made completely free, and then the paper is conveyed by a paper discharge roller.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus applied to an image processing apparatus such as a copying machine, a printer and a facsimile, and more particularly to a sheet conveying technique.

[0002]

2. Description of the Related Art Conventionally, as a general ink jet recording apparatus, a sheet conveying roller is arranged on the upstream side of a recording head,
In some cases, a paper discharge roller is arranged on the downstream side, and recording is sequentially performed corresponding to the conveyance of the paper.

After the paper is fed to the recording head section,
The sheet is mainly fed by the feeding force of the sheet feeding roller, and after the trailing edge of the sheet passes through the sheet feeding roller, the sheet is fed and discharged by the sheet discharging roller.

Further, in order to stabilize the accuracy of the ink landing position and obtain a high recording image quality, the distance between the paper and the recording head is kept constant. The distance between the paper and the recording head is kept constant by holding the paper between the paper transport roller, the pinch roller, the paper discharge roller, and the paper discharge assist roller. Further, in some cases, a sheet pressing member is provided between the sheet conveying roller and the recording head to keep the distance between the sheet and the recording head constant.

[0005]

However, in the conventional ink jet recording apparatus, the sheet is deformed as soon as the sheet passes through the sheet conveying roller or the sheet pressing member,
The distance between the paper and the recording head changes instantly,
In some cases, the image becomes discontinuous and the recorded image quality is significantly deteriorated. This is because, in the case of a high-density image or the like, expansion pressure is generated on the printing surface side, and the trailing edge of the paper curls when it leaves the paper transport roller.

The present invention has been made by paying attention to the above-mentioned problems. When the trailing edge of the sheet is printed, the restraint on the trailing edge of the sheet is gradually released, and finally the trailing edge of the sheet is completely opened. It is an object of the present invention to provide an inkjet recording apparatus having a function of preventing abrupt deformation of a sheet, alleviating discontinuity of an image, and preventing deterioration of a recording image quality by performing printing on the trailing edge of the sheet by Is.

[0007]

In order to solve the above-mentioned problems, the present invention has the following constitutions (1) to (3).

(1) On the upstream side of the recording head in the paper feeding direction, there is a paper regulating means for regulating the height of the paper surface and an open position for releasing the paper, and the paper is arranged upstream of the paper regulating means. And a regulation changing unit that gradually changes the position of the sheet regulation unit from the regulation position to the open position after the sheet detection unit detects the trailing edge of the sheet. An ink jet recording apparatus having a sheet discharging unit.

(2) The recording apparatus according to the above (1), wherein the paper regulating means is a pinch roller facing the paper conveying roller.

(3) The recording apparatus according to the above (1), wherein the paper regulating means is a paper pressing member located between the paper conveying roller and the recording head.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below based on examples with reference to the drawings.

[0012]

Embodiment 1 FIG. 1 shows a serial type ink jet printer which is an example of the configuration of a recording unit section. Reference numeral 1 is a base chassis on which various parts such as a motor are assembled. A paper transport roller 3 that transports the recording paper 2 is driven by a transport motor 5 via a paper drive gear system 4.
The paper discharge roller 13 rotates at the same peripheral speed as the paper transport roller 3 via the friction roller 12. The recording paper 2 is ejected in the direction of arrow A. Recording tank 7 having recording head 6
Are mounted on the carrier 8. The carrier 8 is driven by a carrier motor 9 via a carrier belt 10 along a carrier shaft 11. Predetermined feeding by the paper transport roller 3 and the paper discharge roller 13 and recording scanning of the recording head 6 by scanning of the carrier 8 are repeated.

The motor is driven and controlled by a control board (not shown).

2 and 3 are schematic cross-sectional views of the sheet conveying section in this embodiment.

FIG. 2 shows a normal printing state. In FIG. 2, the sheet 2 is sandwiched between the sheet transport roller 3 and the pinch roller 19, and also sandwiched between the sheet discharge roller 13 and the sheet discharge assist roller 23, and is conveyed in the arrow A direction. The recording head 6 prints in the direction perpendicular to the paper surface every time the paper 2 is fed by one line. In FIG. 2, the paper sensor 15 detects the presence of paper. 1
Reference numeral 4 denotes a paper pressing member, which regulates the maximum height of the paper 2 at the edge of the paper 2 as shown in FIG. This is to prevent contact between the paper 2 and the recording head 6. A pinch roller holder 20 rotatably holds a plurality of pinch rollers 19 as shown in FIG. 4, and is rotatably supported by the base chassis 1 by a holder shaft 22. Reference numeral 18 denotes a pinch spring suspended between the pinch roller holder 20 and the base chassis 1.
Has the effect of urging 17 is a release cam,
The cam gear 21 is integrally formed and is rotatably supported by the base chassis 1. The release cam 17 is rotated by transmitting a driving force to the cam gear 21 by a drive source (not shown). In the state of FIG. 2, the distance between the paper 2 and the recording head 6 is stable and does not change.

FIG. 3 shows a state in which the rear end of the sheet 2 is being printed. In FIG. 3, when the paper sensor 15 detects the absence of paper, that is, the trailing edge of the paper 2, the normal line feed and printing of a predetermined amount are repeated. The predetermined amount may be zero.
When the predetermined amount is reached, the release cam 17 is driven at each line feed,
The pinch roller holder 20 is gradually rotated against the spring force of the pinch spring 18 to separate the pinch roller 19 from the paper transport roller 3. By the time the trailing edge of the sheet 2 reaches the nip portion between the sheet conveying roller 3 and the pinch roller 19, the pinch roller 19 is sufficiently separated from the sheet conveying roller 3 to release the constraint on the trailing edge of the sheet 2. At the time of printing the trailing edge portion, the sheet 2 is conveyed only by the sheet discharge roller 13. Release cam 17 after printing
Is reversely driven to return the pinch roller 19 to the initial position.

By gradually releasing the restraint at the trailing edge of the sheet 2, it is possible to prevent the distance between the sheet 2 and the recording head 6 from abruptly changing, and to avoid discontinuity in the recording image quality.

[0018]

[Embodiment 2] FIGS. 5 and 6 are schematic cross-sectional views of a sheet conveying portion in the present embodiment.

FIG. 5 shows a normal printing state. In FIG. 5, the paper 2 is carried by the paper carrying roller 3 and the pinch roller 24, and is also carried by the paper discharging roller 13 and the paper discharging assist roller 23 in the arrow A direction. Further, the paper surface pressing portion 25 of the paper surface pressing member 16 contacts the paper 2 to hold down the undulation of the paper 2. The recording head 6 prints in the direction perpendicular to the paper surface every time the paper 2 is fed by one line. In FIG. 5, the paper sensor 15 detects the presence of paper. Paper holding member 1
6 and the release cam 17 and the pinch spring 18 are similar in configuration and operation to the first embodiment, and the pinch roller portion of the first embodiment may be replaced with the paper pressing portion. In the state of FIG. 5, the distance between the paper 2 and the recording head 6 remains stable without changing.

FIG. 6 shows a state in which the trailing edge of the sheet 2 is being printed. In FIG. 6, when the paper sensor 15 detects the absence of paper, that is, when the rear end of the paper 2 is detected, line feed and printing are repeated as usual until a predetermined amount. When the predetermined amount is reached, the release cam 17 is driven for each line feed and the pinch spring 18
The paper pressing member 16 is gradually rotated against the spring force of, and the paper pressing portion 25 is separated from the paper. By the time the trailing edge of the sheet 2 reaches the sheet pressing section 25, the sheet pressing section 25 is sufficiently separated from the normal sheet height, and the restraint of the trailing edge of the sheet 2 is released. At the time of printing the trailing edge portion, the sheet 2 is conveyed only by the sheet discharge roller 13. After printing, the release cam 17 is driven to rotate in the reverse direction to return the paper pressing portion to the initial position.

By gradually releasing the constraint at the trailing edge of the sheet 2, it is possible to prevent the distance between the sheet 2 and the recording head 6 from changing rapidly, and to avoid discontinuity in the recording image quality.

[0022]

As described above, according to the present invention,
When printing up to the trailing edge of the paper, the distance between the paper and the recording head does not change abruptly, so discontinuous images do not occur, and good recording image quality is obtained.

[Brief description of drawings]

FIG. 1 is a recording unit section according to an embodiment.

FIG. 2 is a schematic cross-sectional view of a sheet conveying unit according to the first exemplary embodiment.

FIG. 3 is a schematic cross-sectional view of a sheet conveying unit according to the first exemplary embodiment.

FIG. 4 is a block diagram of a pinch roller unit according to the first embodiment.

FIG. 5 is a schematic cross-sectional view of a paper transport unit according to the second embodiment.

FIG. 6 is a schematic cross-sectional view of a sheet conveyance unit according to a second exemplary embodiment.

FIG. 7 is a diagram showing a paper pressing portion of the embodiment.

[Explanation of symbols]

1 base chassis 2 sheets 3 Paper transport rollers 4 Paper drive gear system 5 Conveyor motor 6 recording head 7 recording tank 8 careers 9 Carrier motor 10 Carrier belt 11 Carrier shaft 12 Friction roller 13 Paper ejection roller 14 Paper pressing member 15 Paper sensor 16 Paper holding member 17 Release Cam 18 Cam spring 19 pinch rollers 20 pinch roller holder 21 cam gear 22 Holder shaft 23 Paper ejection assist roller 24 pinch rollers 25 Paper retainer

Claims (3)

[Claims] 1. An upstream side of a recording head in a paper feeding direction,
It has a paper regulating means for regulating the paper surface height and an open position for releasing the paper, and has a paper detecting means upstream of the paper regulating means, and the paper detecting means detects the rear end of the paper. An ink jet recording apparatus comprising: a regulation changing unit that gradually changes the position of the sheet regulation unit from the regulation position to the open position after that; and a sheet unloading unit downstream of the recording head in the sheet feeding direction. 2. The recording apparatus according to claim 1, wherein the paper regulating means is a pinch roller facing a paper conveying roller. 3. The recording apparatus according to claim 1, wherein the paper regulating means is a paper pressing member located between the paper conveying roller and the recording head.